The coal ash is a waste discharged from the coal-combustion power station. The discharge of the coal ash not only occupies a large amount of land, but also pollutes the environment seriously. How to handle and utilize the coal ash becomes a very important problem. The coal ash contains a number of components that can be utilized, such as aluminum oxide, silicon oxide and the like. These useful components, if being extracted, can facilitate a highly efficient complex utilization for the coal ash.
However, during extracting of the useful components of the coal ash, the existence of iron oxide contained in the ash will affect the purity of the extracts. Therefore, it is of great importance to remove iron from the coal ash, for improving the purity of the useful components and improving the complex utilization for the coal ash.
The method of magnetic separation generally used for removing iron from the coal ash is mainly dry magnetic separation, i.e. passing the coal ash through a powerful magnetic separator directly. However, in case of low content of iron impurities (when the content of iron oxide is lower than 5%) in the coal ash, as it is difficult to separate the iron impurities with other coal ash particles, it is thus difficult to remove the iron impurities completely. Therefore, for the coal ash having low iron content, the de-ironing effect by prior methods is unsatisfactory.
Currently, vertical ring magnetic separators are used to select from weak magnetic Iron ore for finally obtaining Iron ore having a certain grade as required. Therefore, their structure and magnetic field strength are designed with respect mainly to iron selecting, not de-ironing. The prior vertical ring magnetic separators have the circular rod shaped stainless steel media as magnetic media, which have relatively large spacing therebetween so as to avoid blocking of the medium rod by the iron ore during magnetically separating. However, during magnetic de-ironing from the coal ash, the spacing between the media is too large, thus the particles in the coal ash which have small granularity and relatively weak magnetism would pass through the media, rather than adsorb by the media, thus decreasing the effect of magnetic separation.
In the traditional magnetic separation applications, the structure of vertical ring magnetic separators are configured to be fed from its upper portion and discharged from its lower portion. However, during de-ironing of the coal ash, as the iron-containing mineral have a relatively weak magnetism, if such upper portion feeding means is employed, it is possible for the iron-containing mineral to penetrate through the media under gravity, rather than being adsorbed, thus further decreasing the effect of magnetic de-ironing.
Therefore, it is necessary to design a new magnetic separation apparatus to overcome the above disadvantageous.